An electron transport layer, perovskite solar cell based thereon and a preparation method

Abstract

This invention discloses an electron transport layer, a perovskite solar cell based thereon, and a preparation method thereof, belonging to the field of solar cell technology. It solves the technical problems of complex fabrication processes and low stability associated with using SnO2-TiO2 hybrid electrodes as electron transport layers. The electron transport layer disclosed in this invention has a SnO2-TiO2-SnO2 sandwich structure or a TiO2-SnO2-TiO2 sandwich structure. By modifying the structure of the electron transport layer without altering its original materials, the resulting sandwich structure theoretically still possesses high transport efficiency. Because the sandwich structure separates SnO2 and TiO2 materials into a sandwich layer, it exhibits higher stability than the hybrid electrode.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to an electron transport layer and a perovskite solar cell based thereon, as well as a method for its fabrication. Background Technology

[0002] With the worsening global climate and the continued depletion of non-renewable energy sources, the utilization of clean and renewable energy is becoming increasingly urgent. Solar energy has attracted much attention due to its cleanliness, large reserves, and wide distribution. With the continuous development of science and technology, researchers have conducted in-depth research and utilization of solar energy. Solar cells account for a large proportion of photovoltaic applications, therefore, research on the materials, performance, and structure of solar cells has gradually received widespread attention.

[0003] In recent years, perovskite solar cells have become a research hotspot due to their advantages such as simple fabrication technology, low cost, and high photoelectric conversion efficiency. Perovskite solar cells can be functionally divided into five layers: an anode layer, a hole transport layer, a light absorption layer, an electron transport layer, and a cathode layer. Among these, the electron transport layer, as a crucial component, plays a key role in extracting and transporting photogenerated electrons, blocking holes, modifying interfaces, regulating interface energy levels, and reducing charge recombination. Because of the relatively complex structure of perovskite solar cells, a simpler electron transport layer is beneficial for practical manufacturing. Furthermore, the composition and structure of the electron transport layer also affect the stability of perovskite solar cells; therefore, research on the structure of the electron transport layer is of great significance. Commonly used materials for electron transport layers (ETLs) include titanium dioxide (TiO2) and tin dioxide (SnO2), which play an important role in nip structure perovskite solar cells. The ETL of flexible perovskite solar cells (f-PSCs) using polymer substrates needs to have strong adhesion to transparent conductive oxide (TCO) and form a uniform thin film at a temperature below 150°C. Prior to this, some researchers prepared SnO2-TiO2 hybrid electrodes as electron transport layers by adding a certain amount of inorganic binder titanium dioxide nanosol to tin dioxide colloidal solution. They found that it exhibited good bending mechanical reliability and greatly improved efficiency due to improved energy alignment. Ultimately, the efficiency of SnO2-TiO2 hybrid electrodes in micro-modules (7×7 cm2-TiO2) reached 21.02%. However, using SnO2-TiO2 hybrid electrodes as electron transport layers is not easy to control the degree of mixing between the two materials, which makes the stability of the hybrid electrodes and actual production more complicated, and not suitable for practical applications. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide an electron transport layer and a perovskite solar cell based thereon and a preparation method thereof, so as to solve the technical problems of complex operation and low stability of the preparation process of SnO2-TiO2 mixed electrode as electron transport layer.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention discloses an electron transport layer, wherein the electron transport layer is a SnO2-TiO2-SnO2 sandwich structure or a TiO2-SnO2-TiO2 sandwich structure;

[0007] The SnO2-TiO2-SnO2 sandwich structure consists of a SnO2 layer, a TiO2 layer, and a SnO2 layer from top to bottom.

[0008] The TiO2-SnO2-TiO2 sandwich structure consists of a TiO2 layer, a SnO2 layer, and a TiO2 layer from top to bottom.

[0009] The present invention also discloses a perovskite solar cell, wherein the perovskite solar cell comprises, from bottom to top, conductive glass, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer and a back electrode layer.

[0010] Furthermore, the conductive glass is ITO conductive glass or FTO conductive glass.

[0011] Furthermore, the ITO conductive glass includes a glass substrate and an ITO conductive layer, wherein the ITO conductive layer is disposed on the upper surface of the glass substrate.

[0012] Furthermore, the hole transport layer is a Spiro-MeOTAD layer; the thickness of the back electrode layer is 70-80 nm; and the material of the back electrode layer is one or more of Al, Ag, Au, Mo, Cr, and C.

[0013] This invention also discloses a method for preparing the above-mentioned perovskite solar cell, comprising the following steps:

[0014] S1: The conductive glass is pretreated to obtain pretreated conductive glass; a first SnO2 hydrocolloid solution coating is applied to the surface of the pretreated conductive glass, followed by annealing, then a TiO2 colloidal solution is applied, followed by annealing, and then a second SnO2 hydrocolloid solution coating is applied. After annealing, an electron transport layer with a SnO2-TiO2-SnO2 sandwich structure is obtained; or a first TiO2 colloidal solution coating is applied to the surface of the pretreated conductive glass, followed by annealing, then a SnO2 hydrocolloid solution is applied, followed by annealing, and then a second TiO2 colloidal solution coating is applied. After annealing, an electron transport layer with a TiO2-SnO2-TiO2 sandwich structure is obtained.

[0015] S2: Mix black phase FAPbI3, MDACl2 and MACl with a mixed solvent composed of dimethylformamide and dimethyl sulfoxide to obtain a perovskite precursor solution. Coat the perovskite precursor solution onto the surface of an electron transport layer with a SnO2-TiO2-SnO2 sandwich structure or an electron transport layer with a TiO2-SnO2-TiO2 sandwich structure. After annealing, a perovskite light-absorbing layer is obtained.

[0016] S3: The Spiro-OMeTAD precursor solution was coated on the surface of the perovskite light-absorbing layer and annealed to obtain the hole transport layer.

[0017] S4: Deposit a back electrode layer on the surface of the hole transport layer.

[0018] Further, in S1, the pretreatment steps for the conductive glass are as follows: the conductive glass is sequentially ultrasonicated with detergent, deionized water, ethanol, and acetone for 20-25 minutes each, then dried with nitrogen and treated in an ultraviolet ozone generator for 15-20 minutes; when preparing the electron transport layer of the SnO2-TiO2-SnO2 sandwich structure, the mass ratio of the first coating SnO2 hydrocolloid solution, the TiO2 colloidal solution, and the second coating SnO2 hydrocolloid solution is 1:2:1; when preparing the TiO2-Sn When constructing the electron transport layer of the O2-TiO2 sandwich structure, the mass ratio of the TiO2 colloidal solution, SnO2 aqueous colloidal solution, and TiO2 colloidal solution in the first coating is 1:2:1; the coating method is spin coating; the spin coating process parameters are: spin coating at 4000-4500 rpm for 40-50 s; the concentrations of the SnO2 aqueous colloidal solution and the TiO2 colloidal solution are 2%-3% respectively; the TiO2 colloidal solution is obtained by reacting hydrogen peroxide with TiO(OH)2 wet cake.

[0019] Further, in S2, the molar percentages of the black phase FAPbI3, MDACl2 and MACl are (0.1-0.2):(3-4):(3-4); the ratio of the amount of the black phase FAPbI3, dimethylformamide and dimethyl sulfoxide is (0.8-0.9) g:(4-5) mL:(4-5) mL.

[0020] Further, in S3, the Spiro-OMeTAD precursor solution is formed from a mixture of chlorobenzene, 4-tert-butylpyridine, lithium bis(trifluoromethanesulfonyl)imide, cobalt TFSI, and acetonitrile; the ratio of chlorobenzene, 4-tert-butylpyridine, lithium bis(trifluoromethanesulfonyl)imide, cobalt TFSI, and acetonitrile is 20–25 μL: 35–40 μL: 23–25 μL: 7–10 μL: 30 μL; in S4, the deposition method is thermal evaporation.

[0021] Furthermore, the annealing treatment is performed at a temperature of 120–130°C for a time of 4–40 minutes.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] This invention discloses an electron transport layer having a SnO2-TiO2-SnO2 sandwich structure or a TiO2-SnO2-TiO2 sandwich structure. By modifying the structure of the electron transport layer without changing its original materials, the resulting sandwich structure electron transport layer theoretically still has high transport efficiency. Since the sandwich structure separates SnO2 and TiO2 materials into a sandwich, it has higher stability than a mixed electrode. Because the existing technology for making stacked electron transport layers is relatively mature, and the process for the sandwich structure electron transport layer is similar, it has good reproducibility and reliability.

[0024] The present invention also discloses a perovskite solar cell based on the above-mentioned electron transport layer. Due to the sandwich structure, the perovskite solar cell has more stable performance. While maintaining high transmission efficiency, it has high stability, making large-scale practical application possible.

[0025] This invention also discloses a method for preparing the aforementioned perovskite solar cell. Compared with the traditional SnO2-TiO2 mixed electrode process, the two materials of the sandwich structure electron transport layer are deposited separately during the preparation of the perovskite solar cell, resulting in better stability. In contrast, the preparation process of the TiO2-SnO2 mixed electron transport layer involves various chemical substances, which may react under certain conditions, thereby affecting some electrical parameters such as the carrier mobility of the electron transport layer. Therefore, theoretically, the sandwich structure electron transport layer is more stable than the mixed electron transport layer. The preparation method disclosed in this invention does not require the preparation of a TiO2-SnO2 mixed solution with a certain concentration, so the preparation process of the sandwich structure is significantly simpler.

[0026] The actual preparation process of this invention is simpler than that of the SnO2-TiO2 mixed electrode process, making it suitable for large-scale industrial production. This preparation process eliminates many factors that need to be considered in the SnO2-TiO2 mixed electrode preparation process, such as some reactions that occur when the mixed solution is affected by factors such as temperature. In addition, the preparation operation of the sandwich structure electrode is simpler and easier, requiring only the following steps for coating, making it more suitable for actual industrial production. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the perovskite solar cell formed by the present invention;

[0028] Figure 2 This is a diagram of the electron transport layer structure of a traditional SnO2-TiO2 hybrid electrode;

[0029] Figure 3 This is a schematic diagram of the electron transport layer structure of the SnO2-TiO2-SnO2 sandwich structure prepared in this invention;

[0030] Figure 4 This is a schematic diagram of the electron transport layer structure of the TiO2-SnO2-TiO2 sandwich structure prepared in this invention. Detailed Implementation

[0031] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0032] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0033] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0034] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0035] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0036] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0037] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0038] Example 1

[0039] A method for fabricating a perovskite solar cell includes the following steps:

[0040] S1: ITO conductive glass was ultrasonically treated with detergent, deionized water, ethanol, and acetone for 20 minutes each, then dried with nitrogen and treated in an ultraviolet ozone generator for 15 minutes to obtain pretreated ITO conductive glass. A 3% (w / w) SnO2 aqueous colloidal solution was used to synthesize a 2.44% (w / w) TiO2 colloidal solution via the reaction of hydrogen peroxide with TiO(OH)2 wet cake. 10g of the TiO2 colloidal solution was spin-coated onto the surface of the pretreated ITO conductive glass. The spin-coating parameters were 4000 rpm for 40 seconds, followed by annealing at 120°C for 30 minutes in ambient air. Then, a SnO2 aqueous colloidal solution, twice the volume of the TiO2 colloidal solution, was spin-coated onto the first TiO2 colloidal solution, again with spin-coating parameters of 4000 rpm for 40 seconds. This was followed by annealing at 120°C for 30 minutes in ambient air, repeating the first TiO2 colloidal solution coating process. This yielded an electron transport layer with a TiO2-SnO2-TiO2 sandwich structure, as shown in the specific structure below. Figure 4 As shown;

[0041] S2: Weigh 0.8g of black phase FAPbI3, MDACl2 and MACl, and dissolve them in a mixed solvent of 4mL dimethylformamide (DMF) and 4mL dimethyl sulfoxide (DMSO) to obtain a perovskite precursor solution; wherein the molar percentage of black phase FAPbI3, MDACl2 and MACl in the perovskite precursor solution is 0.1:3:4. Spin-coat the perovskite precursor solution onto a TiO2-SnO2-TiO2 sandwich structure electrode with spin-coating parameters of 5000 rpm for 30s and anneal at 120℃ for 4min to obtain a perovskite light-absorbing layer.

[0042] S3: A Spiro-OMeTAD precursor solution was prepared by dissolving 20 μL of chlorobenzene (94 mg·mL⁻¹), 39 μL of 4-tert-butylpyridine (TBP), and 23 μL of lithium bis(trifluoromethanesulfonyl)imide (Li TFSI) in 15 μL of acetonitrile (520 mg·mL⁻¹), and 9 μL of cobalt TFSI in 15 μL of acetonitrile (375 mg·mL⁻¹). The obtained Spiro-OMeTAD precursor solution was spin-coated onto a perovskite light-absorbing layer with spin-coating parameters of 3500 rpm for 30 s and annealed at 120 °C for 30 min to obtain the perovskite light-absorbing layer.

[0043] S4: A 70 nm thick aluminum metal electrode was deposited on the perovskite light-absorbing layer using thermal evaporation, resulting in the structure of the perovskite solar cell as shown below. Figure 1 As shown.

[0044] Example 2

[0045] A method for fabricating a perovskite solar cell includes the following steps:

[0046] S1: ITO conductive glass was ultrasonically treated with detergent, deionized water, ethanol, and acetone for 25 minutes each, then dried with nitrogen and treated in an ultraviolet ozone generator for 15 minutes to obtain pretreated ITO conductive glass. A 3% SnO2 hydrocolloid solution was used to synthesize a 2.44% TiO2 colloidal solution via the reaction of hydrogen peroxide with TiO(OH)2 wet cake. 10g of the SnO2 solution was spin-coated onto the surface of the pretreated ITO conductive glass. The parameters were 4500 rpm for 50 seconds, followed by annealing at 130°C for 40 minutes in ambient air. Then, a TiO2 colloidal solution, twice the volume of the SnO2 hydrocolloid solution, was spin-coated onto the SnO2 hydrocolloid solution after the initial spin-coating. The spin-coating parameters were 4000 rpm for 40 seconds, followed by annealing at 120°C for 30 minutes in ambient air. This process was repeated to obtain an electron transport layer with a SnO2-TiO2-SnO2 sandwich structure, as shown in the specific structure below. Figure 3 As shown;

[0047] S2: Weigh 0.9g of black phase FAPbI3, MDACl2 and MACl, and dissolve them in a mixed solvent of 5mL dimethylformamide (DMF) and 5mL dimethyl sulfoxide (DMSO) to obtain a perovskite precursor solution; wherein the molar percentage of black phase FAPbI3, MDACl2 and MACl in the perovskite precursor solution is 0.2:4:3. Spin-coat the perovskite precursor solution onto a TiO2-SnO2-TiO2 sandwich structure electrode with spin-coating parameters of 5000 rpm for 30s and anneal at 120℃ for 4min to obtain a perovskite light-absorbing layer.

[0048] S3: A Spiro-OMeTAD precursor solution was prepared by dissolving 25 μL of chlorobenzene (94 mg·mL⁻¹), 35 μL of 4-tert-butylpyridine (TBP), and 25 μL of lithium bis(trifluoromethanesulfonyl)imide (Li TFSI) in 15 μL of acetonitrile (520 mg·mL⁻¹), and 7 μL of cobalt TFSI in 15 μL of acetonitrile (375 mg·mL⁻¹). The obtained Spiro-OMeTAD precursor solution was spin-coated onto a perovskite light-absorbing layer with spin-coating parameters of 3500 rpm for 30 s and annealed at 120 °C for 30 min to obtain the perovskite light-absorbing layer.

[0049] S4: An 80 nm thick silver metal electrode was deposited on the perovskite light-absorbing layer using thermal evaporation, resulting in the structure of the perovskite solar cell as shown below. Figure 1 As shown.

[0050] Example 3

[0051] A method for fabricating a perovskite solar cell includes the following steps:

[0052] S1: ITO conductive glass was ultrasonically treated with detergent, deionized water, ethanol, and acetone for 25 minutes each, then dried with nitrogen and treated in an ultraviolet ozone generator for 15 minutes to obtain pretreated ITO conductive glass. A 2.44% TiO2 colloidal solution was synthesized using a 3% SnO2 hydrocolloid solution via the reaction of hydrogen peroxide with TiO(OH)2 wet cake. 10g of the SnO2 hydrocolloid solution was spin-coated onto the surface of the pretreated ITO conductive glass. The coating parameters were 4300 rpm for 45 seconds, followed by annealing at 125°C for 10 minutes in ambient air. Then, twice the volume of the SnO2 hydrocolloid solution was used as the TiO2 colloidal solution for spin coating on top of the first SnO2 hydrocolloid solution spin coating, with spin coating parameters of 4000 rpm for 40 seconds. This was followed by annealing at 120°C for 30 minutes in ambient air, repeating the first SnO2 hydrocolloid solution coating process. This yielded an electron transport layer with a SnO2-TiO2-SnO2 sandwich structure, as shown in the specific structure below. Figure 3 As shown;

[0053] S2: Weigh 0.9 g of black phase FAPbI3, MDACl2 and MACl, and dissolve them in a mixed solvent of 4 mL dimethylformamide (DMF) and 5 mL dimethyl sulfoxide (DMSO) to obtain a perovskite precursor solution; wherein the molar percentage of black phase FAPbI3, MDACl2 and MACl in the perovskite precursor solution is 0.2:3:3. Spin-coat the perovskite precursor solution onto a TiO2-SnO2-TiO2 sandwich structure electrode with spin-coating parameters of 5000 rpm for 30 s and anneal at 120 °C for 4 min to obtain a perovskite light-absorbing layer.

[0054] S3: A Spiro-OMeTAD precursor solution was prepared by dissolving 25 μL of chlorobenzene (94 mg·mL⁻¹), 35 μL of 4-tert-butylpyridine (TBP), and 25 μL of lithium bis(trifluoromethanesulfonyl)imide (Li TFSI) in 15 μL of acetonitrile (520 mg·mL⁻¹), and 7 μL of cobalt TFSI in 15 μL of acetonitrile (375 mg·mL⁻¹). The obtained Spiro-OMeTAD precursor solution was spin-coated onto a perovskite light-absorbing layer with spin-coating parameters of 3500 rpm for 30 s and annealed at 120 °C for 30 min to obtain the perovskite light-absorbing layer.

[0055] S4: A 75 nm thick metal electrode Cr was deposited on the perovskite light-absorbing layer using a thermal evaporation method.

[0056] Comparative Example 1

[0057] A method for fabricating a perovskite solar cell includes the following steps:

[0058] 1) Cleaning glass: For ITO or FTO glass, use detergent, deionized water, ethanol, and acetone, respectively, and sonicate for 20 minutes each. After drying with nitrogen, treat in a UV ozone generator for 15 minutes.

[0059] 2) Preparation of the electron transport layer: First, a mixed solution was prepared by mixing equal volumes of two solutions: a SnO2 colloidal solution with a mass fraction of 3% and a TiO2 colloidal solution with a mass fraction of 2.44%. The prepared TiO2-SnO2 mixed solution was then spin-coated onto an ITO substrate at 4000 rpm for 40 seconds, followed by annealing at 120°C for 30 minutes in ambient air. The specific structure is shown below. Figure 2 As shown;

[0060] 3) Preparation of perovskite light-absorbing layer: The perovskite precursor solution was prepared by mixing black phase FAPbI3 (810 mg) with MDACl2 (3.8 mol%) and MACl (3.5 mol%). The reagents were weighed according to the ratio and dissolved in a mixed solvent of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) with a solvent volume ratio of 8:1. The prepared perovskite precursor solution was spin-coated onto a TiO2-SnO2 mixed electrode with spin-coating parameters of 5000 rpm for 30 s and annealed at 120℃ for 40 min.

[0061] 4) Hole transport layer preparation: First, when preparing the Spiro-OMeTAD precursor solution, 4-tert-butylpyridine (TBP) and lithium bis(trifluoromethanesulfonate)imide (Li-TFSI) are usually doped. The prepared Spiro-OMeTAD transport layer needs to undergo a redox reaction with oxygen to have better photoelectric conversion efficiency. The prepared Spiro-OMeTAD precursor solution is spin-coated onto the perovskite light absorption layer with spin-coating parameters of 3500 rpm for 30 s and annealing at 120°C for 30 min.

[0062] 5) Fabrication of metal electrode: A 70 nm thick metal electrode was deposited on the perovskite light-absorbing layer by thermal evaporation.

[0063] A comparison of the stability and fabrication steps of the perovskite solar cells prepared in the above-mentioned comparative examples and two examples reveals that the fabrication process of the two sandwich-structured electron transport layer perovskite solar cells does not require the preparation of a TiO2-SnO2 mixed solution with a specific concentration, thus significantly simplifying the sandwich structure fabrication process. Furthermore, the two materials of the sandwich structure electron transport layer are deposited separately during the fabrication of the perovskite solar cell, resulting in better stability. In contrast, the fabrication process of the TiO2-SnO2 mixed electron transport layer involves various chemical substances, which may react under certain conditions, affecting electrical parameters such as carrier mobility. Therefore, theoretically, the sandwich structure electron transport layer is more stable than the mixed electron transport layer.

[0064] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a perovskite solar cell, characterized in that, Includes the following steps: S1: Pre-treat the conductive glass to obtain pre-treated conductive glass; The conductive glass surface of the pretreated conductive glass is first coated with a SnO2 hydrocolloid solution, then annealed, then coated with a TiO2 colloidal solution, annealed, and then coated with a second SnO2 hydrocolloid solution. After annealing, an electron transport layer with a SnO2-TiO2-SnO2 sandwich structure is obtained; or the conductive glass surface of the pretreated conductive glass is first coated with a TiO2 colloidal solution, then annealed, then coated with a SnO2 hydrocolloid solution, annealed, and then coated with a second TiO2 colloidal solution. After annealing, an electron transport layer with a TiO2-SnO2-TiO2 sandwich structure is obtained. S2: Mix black phase FAPbI3, MDACl2 and MACl with a mixed solvent composed of dimethylformamide and dimethyl sulfoxide to obtain a perovskite precursor solution. Coat the perovskite precursor solution onto the surface of an electron transport layer with a SnO2-TiO2-SnO2 sandwich structure or an electron transport layer with a TiO2-SnO2-TiO2 sandwich structure. After annealing, a perovskite light-absorbing layer is obtained. S3: The Spiro-OMeTAD precursor solution was coated on the surface of the perovskite light-absorbing layer and annealed to obtain the hole transport layer. S4: Deposit a back electrode layer on the surface of the hole transport layer; The perovskite solar cell consists of, from bottom to top, conductive glass, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer, and a back electrode layer. The conductive glass is ITO conductive glass or FTO conductive glass. The ITO conductive glass includes a glass substrate and an ITO conductive layer, wherein the ITO conductive layer is disposed on the upper surface of the glass substrate; The hole transport layer is a Spiro-MeOTAD layer; the thickness of the back electrode layer is 70~80nm; the material of the back electrode layer is one or more of Al, Ag, Au, Mo, Cr and C; The electron transport layer is a SnO2-TiO2-SnO2 sandwich structure or a TiO2-SnO2-TiO2 sandwich structure; The SnO2-TiO2-SnO2 sandwich structure consists of a SnO2 layer, a TiO2 layer, and a SnO2 layer from top to bottom. The TiO2-SnO2-TiO2 sandwich structure consists of a TiO2 layer, a SnO2 layer, and a TiO2 layer from top to bottom.

2. The method for preparing a perovskite solar cell according to claim 1, characterized in that, In S1, the pretreatment steps for the conductive glass are as follows: the conductive glass is sequentially ultrasonicated with detergent, deionized water, ethanol, and acetone for 20-25 minutes each, then dried with nitrogen and treated in an ultraviolet ozone generator for 15-20 minutes; when preparing the electron transport layer of the SnO2-TiO2-SnO2 sandwich structure, the mass ratio of the first coating SnO2 hydrocolloid solution, TiO2 colloidal solution, and the second coating SnO2 hydrocolloid solution is 1:2:1; when preparing the TiO2-SnO2- When constructing the electron transport layer of the TiO2 sandwich structure, the mass ratio of the TiO2 colloidal solution, SnO2 aqueous colloidal solution, and TiO2 colloidal solution in the first coating is 1:2:1; the coating method is spin coating; the spin coating process parameters are: spin coating at 4000~4500 rpm for 40~50 s; the concentrations of the SnO2 aqueous colloidal solution and the TiO2 colloidal solution are 2%~3% respectively; the TiO2 colloidal solution is obtained by reacting hydrogen peroxide with TiO(OH)2 wet cake.

3. The method for preparing a perovskite solar cell according to claim 1, characterized in that, In S2, the molar percentages of the black phase FAPbI3, MDACl2 and MACl are (0.1~0.2):(3~4):(3~4); the ratio of the amount of the black phase FAPbI3, dimethylformamide and dimethyl sulfoxide is (0.8~0.9) g:(4~5) mL:(4~5) mL.

4. The method for preparing a perovskite solar cell according to claim 1, characterized in that, In S3, the Spiro-OMeTAD precursor solution is formed from a mixture of chlorobenzene, 4-tert-butylpyridine, lithium bis(trifluoromethanesulfonyl)imide, cobalt TFSI, and acetonitrile; the ratio of chlorobenzene, 4-tert-butylpyridine, lithium bis(trifluoromethanesulfonyl)imide, cobalt TFSI, and acetonitrile is 20~25µL:35~40µL:23~25µL:7~10µL:30µL; in S4, the deposition method is thermal evaporation.

5. The method for preparing a perovskite solar cell according to claim 1, characterized in that, The annealing process is performed at a temperature of 120-130°C for 4-40 minutes.

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